Compare the KJV with the NASB.
(Proverbs 23:16 NAS77) And my inmost being will rejoice, When your lips speak what is right.Notice that one has “reins” (3629) and the other has “inmost being”. What caught my attention was the marginal reading of the NASB which said, “literally kidneys”. That is the basic meaning of the word and is the most common translation in both. We get very romantic when we talk about our heart but somehow moderns don’t get excited about their kidneys. Maybe we should.
Solomon here is telling his son that if he will learn to speak what is “right” (4339) it will make dad’s kidneys happy. I don’t think this is a literal teaching about medicine. The Hebrews knew what a kidney was even if they didn’t know all the scientific stuff we know today. It was the location that was important. A son who learns to speak what is right is a son that gives his father an inner sense of rightness.
So? The training is up to the parents. The results are on the heads of the children. My kids are adults and I can say that the effects continue.